The present invention relates to the art of portable emergency breathing apparatus and, more particularly, to improvements in connection with breathing apparatus of the character in which breathing gas is re-breathed.
Breathing apparatus of the character wherein exhaled breath of a user is mixed with oxygen from a supply container, scrubbed to reduce the concentration of exhaled carbon dioxide, and re-breathed by the user is generally referred to as closed circuit breathing apparatus. The primary advantage of such apparatus over open circuit apparatus wherein oxygen under pressure from a container is continuously supplied to a hood or face mask worn by the user and wherein the air breathed by the user is exhaled to atmosphere, is the fact that closed circuit apparatus enables optimizing the duration of use thereof with a given sized compressed oxygen container. At the same time, such apparatus presently available is comprised of a considerable number of component parts which, as a result of the size, cost and structural inter-relationship therebetween results in the apparatus being undesirably expensive, large in overall dimensions and heavy. Furthermore, such apparatus heretofore available have exposed component parts which are subject to easy damage and this, together with the weight and size, makes the apparatus undesirable in certain environments of potential use. More particularly with regard to such disadvantages, the compressed oxygen cylinder and scrubber components of the apparatus have been structurally separate components disposed side-by-side or, in some instances, completely separate from one another and interconnected by elaborate flow line systems. With regard to flow control valve arrangements for such apparatus which generally includes a shutoff valve, a pressure reducing valve and a demand valve for supplying air from the compressed air cylinder in response to the user's breathing, these valves heretofore have been structurally separate components mounted at different locations within the confines of the apparatus. Accordingly, it will be appreciated that the cost of the apparatus is affected by having to provide two or three structurally independent valves, by having to provide fittings for mounting the valves, and by the time required in connection with assembly of the apparatus.
One previous effort to provide a compact, light weight closed circuit re-breathing device is disclosed in U.S. Pat. No. 3,208,449 to Bartlett. The Bartlett apparatus is characterized by the wrapping of tubing around a scrubber canister to provide a compressed oxygen source. The canister is directly attached to a face mask, and a breathing bag is attached to the bottom of the canister. While achieving compactness, the Bartlett arrangement does not overcome the other disadvantages referred to hereinabove and, additionally, introduces other disadvantages. In this respect, without regard to the quantity of oxygen which the tubing is capable of holding, external exposure of the tubing is disadvantageous from the standpoint of potential damage or rupture either prior to or during use and, during use in an emergency situation such as a fire, undesirably exposes the stored oxygen directly to ambient heat and thus the potential that the user will be breathing hot air. With regard to the other disadvantages referred to hereinabove, the Bartlett unit requires structurally separate pressure reducing and demand valves, and the pressure reducing valve and a pressure gauge for the unit are exposed laterally of the unit and in locations subjecting these components to potential damage, again either prior to or during use. A further disadvantage resides in the fact that the entire unit is supported on the head of the user through the face mask which, regardless of the lightness of weight, is both uncomfortable for the user and restricts movement of the head of the user from side-to side without potentially dislodging the mask from its position over the user's face by engagement of the depending apparatus with the user's chest and shoulders.